In chapter 17, God more formally makes an agreement—a covenant—with Abraham, presenting its terms in a general way.
Abraham was to be perfect. Other Bibles translate this term as "upright," "blameless," or "sincere." Do not be misled by the word "sincere," because its meaning has changed over the years. To us, it simply means that we have good intentions, but that is not really what the word means. It actually means "without flaw," that is, no imperfections.
Under the covenant, Abraham had to meet some conditions. He had to live a life of obedience. He had to submit to God. God raised the standard so high for him, that one would almost think that he had to be without sin.
Perhaps this begins to bring something else to mind, say, Jesus' command in the Sermon on the Mount to be "perfect, even as your Father in heaven is perfect." "Perfect" can also be translated "mature" or "complete." It is very similar to what God said to Abraham. What is Jesus doing? He is beginning to introduce concepts that are part of both the Abrahamic Covenant and the New Covenant.
Abraham is very plainly called "the father of the faithful," as if he were the head of the family of all who have ever lived, with the exception of Jesus Christ, who is the model after which we are to mold ourselves. Jesus was not human in quite the same way as Abraham was and the rest of us are. He was "God in the flesh" while we are just "flesh" who have the gift of God's Spirit. He had the Spirit without measure, but we have to grow in it. He had to grow too, but there is a qualitative difference. Nevertheless, according to Galatians 3, if we are Christ's, we are Abraham's seed and heirs according to the promise.